Chemical cleaning compounds have long been advantageously used in a variety of contexts. Such compounds are produced in solid, granulated or powdered, and liquid forms. Typically, a cleaning compound is mixed with a solvent (e.g., water) to form a cleaning solution. The present invention is broadly directed to methods and apparatus for precisely mixing a solvent and a detergent to form a liquid detergent solution.
One particularly popular class of chemical cleaning compounds is produced in solid, granulated or powdered form and is mixed with a solvent, carrier or dispersent prior to use. For ease of discussion, the term solid is defined herein to include the terms granulated and powdered. This is justified since all three forms or states include a solid chemical cleaning compound. The present discussion is directed primarily to dispensing cleaning solutions made from solid detergents. However, the present invention is not in any way limited to solid detergent applications.
In addition, the following description will refer to the liquid which is mixed with the solid as a solvent, though the invention is not limited to dispensing "solutions" in the strict sense of the word. Mixtures, slurries, suspensions and the like are also contemplated. Since water is a very common solvent, the following discussion will be directed primarily to methods and apparatus for mixing water with a solid detergent to form a liquid detergent solution.
One very common use for detergent solutions formed from solid detergent dissolved in water is for dishwashing, and this example will be used to describe the prior art and preferred embodiments of the present invention. It should be emphasized that the present invention is not limited to dishwashing applications, however. In dishwashing applications, the liquid cleaning or detergent solution, a solution in which the concentration of detergent is quite high, is typically mixed with water in a sink in which dishes are washed. It has long been recognized that an optimum ratio of liquid detergent solution to water exists. Choosing the "optimum" ratio involves a consideration of factors such as the cost of the cleaner, the temperature of the water, and the "soil load" of the dishes to be washed.
Still focusing on the dishwashing example, one method by which an optimum ratio of water to liquid detergent solution can be achieved is by precisely measuring the water within the sink and adding to the water the appropriate amount of liquid cleaning solution. One way to ensure that the appropriate amount of cleaning solution has been added to the sink is to allow the liquid cleaning solution to flow to the sink for a predetermined period of time. The present invention is particularly directed to a method and means for metering, dispensing or producing a precise amount of liquid detergent solution by opening a valve between a pressurized water source and a solid cleaning compound for a precise predetermined length of time.
It is perceived that one very desirable characteristic of such a cleaning solution dispensing system is that it be self-contained. That is, it is very desirable that the dispensing system not require connection to a central source of power, e.g., line voltage supplied by an electrical utility. Self-containment provides for a simpler installation, making for a less expensive cleaning solution dispenser. For example, if a dispensing system does not require connection to line voltage, the installation need not be done by an experienced electrician. Furthermore, self-containment results in a dispensing system that is more fool-proof. In addition, if the dispensing system is self-contained there is one fewer connection that is subject to failure and the system can more thoroughly be checked at the factory prior to installation in the field. Additionally, surge surpressers and the like need not be included in the system to filter line surges since the system is internally powered and controlled.
It is also desirable that the liquid detergent solution producing apparatus be inexpensive. In many cases the liquid detergent solution producing apparatus is used in conjunction with a fairly small dishwashing system and high cost must be avoided.
Another desirable characteristic of such a cleaning solution dispensing system is that it be accurate and precise. If too much liquid cleaning solution is delivered to a cleaning station (e.g., a sink), excessive foaming can result, cleaning solution is effectively wasted, and cleaning efficiency is not proportionally increased. If, on the other hand, too little cleaning solution is dispensed, cleaning efficiency suffers and energy is wasted since multiple cleanings may be needed.
Still another attribute of a preferred liquid cleaning solution dispenser is simplicity, to minimize cost and increase the mean time between failures.
The prior art does not disclose a liquid detergent dispensing system having all of the attributes discussed above. One fairly standard cleaner dispensing system includes a spring-loaded normally-closed solenoid-operated valve that requires continuous electrical power during the period of time that the valve is held open to dispense the liquid cleaning solution. This type of valve naturally requires a comparatively large amount of energy and makes self-containment essentially unachievable. Other electrical control systems have been contemplated, but in many cases such systems are prohibitively complex and costly. Further, very often such systems are too delicate for rugged industrial applications.
In view of these potential problems with electrical control systems, the present invention is directed to a fluid-operated system. The present invention uses a timing fluid (e.g., paraffin or mineral oil) to control the rate of closure of a normally closed valve that has typically been manually opened Such a system can be selfcontained; inexpensive; simple; and essentially fool-proof. Therefore, it is perceived that the present invention is directed to and solves many of the problems addressed above.
As noted above, the present invention provides for a detergent solution dispensing system that can be completely self-contained. Preferred systems constructed according to principles of the present invention are thus relatively simple to install and need not have built-in filters or the like to guard against transient behavior in central power supplies. Additionally, apparatus of the present invention can be easily and safely installed without requiring the services of an electrician. Systems according to the present invention can be easily installed in locations where central power is not conveniently accessible. Furthermore, preferred apparatus, being self-contained, are not limited to a particular line voltage or solvent pressure, and can therefore be installed domestically without including means for accommodating local voltage variations, and internationally with no modifications to account for the varying line characteristics worldwide.